According to the ADA acceptance program for posterior composite materials, occlusal wear should not exceed 250 Mum during a five year period of clinical service. To determine this amount of wear, either comparison with standards or profile mapping of the surface with a stylus are suggested. The limitations of these techniques are that they either use a poorly defined reference plane or that the samples representing different states of wear must be mounted in identical positions. In addition, both methods lack the ability to relate local wear changes to micro-morphological changes. Improved methods of wear measurement require: 1) the establishment of a fixed reference plane, 2) an insensitivity to specimen positioning, 3) the quantitation of localized wear, and 4) the capability to analyze local micro-morphological changes. The first objective of this project is to develop a system capable of performing stereophotogrammetric measurements on SEM photographs and transfer these measurements to a microcomputer capable of producing 3-D plots of the investigated surface. Fixed anatomic landmarks will be chosen for the determination of a reference plane. Thus, local changes in the distance between the investigated surface and the reference plane can be identified and quantified. When such a local change has been located, the morphology of this region can be determined from the SEM photographs. The second objective is to compare the proposed technique with a method based on visual comparison with standards. Five dentists will estimate the depth of grooves cut into metal surfaces by comparison with standards. Following this estimation, the SEM stereophotogrammetric method will be used to determine the depth of these grooves. The results of these two determinations will be compared and the reliability of the SEM stereophotogrammetric method will be evaluated for potential studies of composite resin wear.